This problem can occur when you use the Mac migration tool to move Prism from one computer to another. Update to the latest release using Help.Check for updates.
Releases of Prism 6.0a, 6.0b and 6.0c will not install properly under Mavericks, or Yosemite and you'll see the message about inability to save the serial number file.
If you use early releases of Prism 6 with Mavericks or Yosemite There is a very high chance this will solve the problem.
